An integrated circuit may include source/drain symmetric MOS transistors which are structurally symmetric with respect to their source and drain nodes, and source/drain asymmetric MOS transistors such as drain extended MOS (DEMOS) or laterally diffused MOS (LDMOS) transistors which have drain structures capable of operating at higher voltages than the symmetric MOS transistors. The asymmetric MOS transistors may require thicker gate dielectric layer than the symmetric MOS transistors to provide desired levels of performance, such as on-state drive current and off-state leakage current, from each transistor. It may also be desirable to minimize the photolithographic operations performed during fabrication of the integrated circuit.